Back Up Alarm problems of the 2006 Chrysler Pacifica

Rear (backup) sensor intermittently inoperative (led to non-injury crash); default factory settings error. Left home yesterday evening, backup sensor was working (alerted driver to truck in drive and tree near driveway). Drove to destination (<2 m. ) and parked vehicle on street. Left destination about 3 hours later, bound for another residence to pick up our daughter (. 5 m). It was a very dark and rainy night, no street lights. Drove into residential driveway, then backed out of driveway. Upon backing onto street, rear bumper of Pacifica hit front bumper of small, dark blue, Lincoln sedan parked on street. The backup sensor did not work at all. There were no injuries, and only minor damage (although needless) to the bumpers. However, this is potentially a very dangerous equipment failure. We checked the control menus. *factory settings* was *, and, within these settings, *park assist system* was *. We (my husband or I) had not changed the settings, and, as mentioned, the sensor had worked earlier that evening. The same ignition key was used for all driving that evening. We checked the settings because of a similar incident two weeks earlier (see below). Two weeks ago, after a short drive from home (<3 m. ), we noticed the backup sensor was not working when we were backing out of a parking space, although it had been working earlier in the day. As in the later incident, the *factory settings* setting was *, and, within these settings, *park assist system* was *. We (my husband or I) had not changed the settings. We were befuddled as to the reason this happened. We set the *factory settings* back to *, and confirmed that this reset the *park assist system* to *. The rear sensor then seemed to be working okay, until the recurrence of the problem last night. I will talk to the dealer about this problem tomorrow (closed today), so I have no info on mfg actions to correct this failure.